Cellular Respiration Quiz

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Questions and Answers

What is the final product of the oxidation of acetylCoA during cellular respiration?

  • ATP
  • CO2 (correct)
  • FADH2
  • NADH

Which stage of cellular respiration involves oxidative phosphorylation?

  • Oxidation of organic fuels to acetylCoA
  • Conversion of ATP to ADP
  • Oxidation of electron carriers with O2 (correct)
  • Conversion of acetylCoA to CO2 and electron carriers

What type of reaction is catalyzed by the pyruvate dehydrogenase complex?

  • Reversible decarboxylation
  • Irreversible phosphorylation
  • Irreversible decarboxylation (correct)
  • Reversible phosphorylation

What is the role of O2 in cellular respiration?

<p>Final electron acceptor (C)</p> Signup and view all the answers

Where does cellular respiration primarily occur within the cell?

<p>Mitochondria (D)</p> Signup and view all the answers

What is the main function of the PDH complex?

<p>Converts pyruvate to acetyl Co-A (C)</p> Signup and view all the answers

Which of the following vitamins is NOT involved as a cofactor in the PDH complex?

<p>Folic acid (B9) (B)</p> Signup and view all the answers

How does lipoic acid function within the PDH complex?

<p>It can undergo redox reactions and attach acetyl groups (D)</p> Signup and view all the answers

What effect does phosphorylation have on the PDH complex?

<p>It makes PDH less active (A)</p> Signup and view all the answers

Which of the following is a result of chronic decreased activity of PDH?

<p>Chronic Lactic Acidosis (CLA) (C)</p> Signup and view all the answers

What characterizes acetyl Co-A in comparison to ATP?

<p>It is more energy-rich than ATP (A)</p> Signup and view all the answers

Which enzymes are involved in modifying the activity of the PDH complex?

<p>PDH-kinase and PDH-phosphatase (D)</p> Signup and view all the answers

What is the primary product when citrate undergoes isomerization in the citric acid cycle?

<p>Isocitrate (B)</p> Signup and view all the answers

Which compound acts as the final electron acceptor in the electron harvesting process after FADH2 conversion?

<p>NAD+ (B)</p> Signup and view all the answers

What is the main function of anaplerotic reactions in the citric acid cycle?

<p>To replenish citric acid cycle intermediates (B)</p> Signup and view all the answers

Which molecule is formed when malate is oxidized in the final step of the citric acid cycle?

<p>Oxaloacetate (C)</p> Signup and view all the answers

Which of the following describes the amphibolic nature of the TCA cycle?

<p>It acts both as an energy-producing and a biosynthetic pathway. (A)</p> Signup and view all the answers

What is the primary role of the PDH complex in cellular metabolism?

<p>To convert pyruvate to acetylCoA (C)</p> Signup and view all the answers

Which enzyme in the PDH complex is responsible for the decarboxylation of pyruvate?

<p>Pyruvate dehydrogenase (D)</p> Signup and view all the answers

What coenzyme is utilized by the E1 enzyme during the decarboxylation of pyruvate?

<p>Thiamine pyrophosphate (TPP) (A)</p> Signup and view all the answers

What is released as a byproduct during the decarboxylation of pyruvate?

<p>Carbon dioxide (CO2) (C)</p> Signup and view all the answers

What type of reaction occurs when the acetaldehyde is transferred to the lipoyl moiety of E2?

<p>Internal redox reaction (D)</p> Signup and view all the answers

What is the function of the swinging lipoyl arm in the PDH complex?

<p>Connect E1 and E3 actively (B)</p> Signup and view all the answers

Which component is NOT part of the PDH complex?

<p>Acetyl CoA synthase (B)</p> Signup and view all the answers

What happens after the free thiamine is released during the PDH process?

<p>It is available to accept another pyruvate (C)</p> Signup and view all the answers

What is the structure of E2 in the PDH complex?

<p>Trimeric (D)</p> Signup and view all the answers

Which of the following best describes the coupling of PDH complex enzymes?

<p>They are mechanically coupled. (C)</p> Signup and view all the answers

Flashcards

Cellular Respiration

The aerobic phase of catabolism where cells consume oxygen, produce carbon dioxide, and generate energy.

Pyruvate Dehydrogenase Complex (PDH)

A cluster of enzymes that catalyze the oxidative decarboxylation of pyruvate to acetyl CoA, an irreversible process.

Citric Acid Cycle Stages

Cellular respiration comprises three stages: oxidation of fuels to acetylCoA, conversion of acetylCoA to CO2 and reduced electron carriers, and oxidation of electron carriers.

Mitochondria

Cellular organelles where cellular respiration occurs.

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Acetyl CoA

A molecule formed from pyruvate, acting as fuel for the latter stages of cellular respiration.

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PDH Complex

A complex of enzymes that converts pyruvate to acetyl CoA, releasing CO2 and NADH.

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Pyruvate

A 3-carbon molecule, precursor to Acetyl-CoA in cellular respiration.

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Acetyl CoA

A 2-carbon molecule, product of the PDH complex and important for the Citric Acid Cycle.

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Lipoic Acid

A crucial cofactor in the PDH complex, participating in redox reactions and acetyl group transfers.

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PDH Complex Enzymes

The PDH complex is composed of three enzymes that catalyze the conversion of pyruvate to acetyl CoA.

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Cofactors in PDH Complex

TPP, lipoic acid, NAD+, FAD, and CoA-SH are five coenzymes needed for the PDH complex's function.

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Chronic Lactic Acidosis (CLA)

Inherited condition arising from decreased PDH activity, leading to lactic acid buildup because pyruvate cannot be converted to acetyl-CoA.

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Citric Acid Cycle (TCA)

A metabolic pathway that oxidizes acetyl-CoA to CO2, generating ATP and electron carriers.

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Acetyl-CoA

A molecule that carries acetyl groups into the citric acid cycle.

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Lipoic Acid

A coenzyme crucial for redox reactions in the PDH complex (and TCA cycle).

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Dihydrolipoyl dehydrogenase (E3)

enzyme that regenerates oxidized lipoic acid in the PDH complex (and TCA cycle).

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Anaplerotic reactions

Reactions that replenish citric acid cycle intermediates.

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Pyruvate Decarboxylation

Conversion of pyruvate to acetyl CoA, releasing carbon dioxide. A crucial step in cellular respiration.

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PDH complex

A large enzyme complex catalyzing the conversion of pyruvate to acetyl CoA.

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TPP (Thiamine pyrophosphate)

A coenzyme that facilitates the initial decarboxylation step.

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Lipoyl Arm

Part of enzyme E2 that carries intermediates between enzymes in PDH complex.

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Acetaldehyde

Intermediate molecule in conversion of pyruvate to acetate.

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Enzyme E1 (Pyruvate Dehydrogenase)

Decarboxylates pyruvate using TPP, producing hydroxyethyl-TPP.

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Enzyme E2 (Dihydrolipoyl Transacetylase)

Transfers the acetyl group from hydroxyethyl-TPP to CoA, making acetyl CoA

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Enzyme E3 (Dihydrolipoyl Dehydrogenase)

Regenerates the oxidized form of lipoyl of E2 (with FAD).

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Acetyl CoA

A key molecule, carrying acetyl group to the citric acid cycle, provides energy.

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Redox Reaction (Step 2)

Oxidation of acetaldehyde to acetate

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